The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform
Joris Degrieck - One of the best experts on this subject based on the ideXlab platform.
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novel pure shear Sheet Specimen geometry for dynamic material characterisation
DYMAT 2009 - 9th International Conferences on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, 2009Co-Authors: Jan Peirs, Wim Van Paepegem, Patricia Verleysen, Joris DegrieckAbstract:A novel Sheet Specimen geometry for dynamic pure-shear experiments is proposed. Finite element simulations in ABAQUS/Explicit are used to optimize the Specimen geometry. Main objective is to obtain a homogeneous stress state with a low stress tridxiality in the Specimen zone subjected to shear. The proposed geometry is used to characterize the dynamic shear behaviour of a Ti-6Al-4V alloy. High speed photography and digital image correlation are used to study the local behaviour of the Specimen. The experiments are compared with the simulations. It is found that the maximal strain reached is higher than in tensile tests of this material. The shear experiments thus provide valuable information for material modelling.
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experimental investigation of the deformation of hopkinson bar Specimens
International Journal of Impact Engineering, 2004Co-Authors: Joris DegrieckAbstract:Split Hopkinson bar (SHB) experiments are often used to study the strain rate dependent mechanical properties of materials. During a SHB experiment a small sample of the material under study is subjected to a high strain rate, uni-axial, tensile, compressive or torsion load. From the classical measurements the time history of the mean stress, strain rate and strain in the Specimen can be derived. For some applications, more detailed information concerning the variation of the deformation in the Specimen is necessary. In this contribution a technique is presented which makes it possible to obtain the deformation along the length of the Specimen. The deformation of a line grid attached to the Specimen is recorded during an experiment by means of a streak camera. An advanced and innovative numerical technique, based on a combination of geometric moire and phase shifting, is developed to extract the time history of the deformation along the axis of the Specimen from the picture of the deforming grid automatically. Large Specimen deformations are allowed, and the technique proved to give highly accurate results. In this contribution results are presented of a SHB experiment on a steel Sheet Specimen. Some remarks are formulated concerning the generally assumed homogeneity of the deformation in the Specimen, and the deformation obtained with the classical measurement techniques.
Ikuya Kurosaki - One of the best experts on this subject based on the ideXlab platform.
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tension compression asymmetry of phosphor bronze for electronic parts and its effect on bending behavior
International Journal of Plasticity, 2009Co-Authors: Toshihiko Kuwabara, Yutaka Kumano, Jindra Ziegelheim, Ikuya KurosakiAbstract:Abstract In-plane tension and compression experiments on copper alloy Sheets (phosphor bronze) and 6000 series aluminum alloy Sheets (AA6016-T4) were conducted using a specially designed testing apparatus. The apparatus is equipped with comb-type dies so that stress–strain curves of a Sheet Specimen subjected to tension followed by compression, and vice versa, can be measured without buckling of the Specimen, as well as those for monotonic tension and compression. A difference was observed in the flow stresses between tension and compression for the as-received copper alloy, but not for the aluminum alloy. Moreover, stress reversal tests, such as tension followed by compression and compression followed by tension, were carried out in order to measure the Bauschinger effect. In the second part of the experiment, bending moment–curvature diagrams were measured for the as-received and pre-stretched Specimens. The bending moment–curvature diagrams were compared with those calculated using the stress–strain curves obtained from the tension–compression tests, and were in good agreement with those calculated with the tension–compression asymmetry and the Bauschinger effect correctly reproduced.
Toshihiko Kuwabara - One of the best experts on this subject based on the ideXlab platform.
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tension compression asymmetry of phosphor bronze for electronic parts and its effect on bending behavior
International Journal of Plasticity, 2009Co-Authors: Toshihiko Kuwabara, Yutaka Kumano, Jindra Ziegelheim, Ikuya KurosakiAbstract:Abstract In-plane tension and compression experiments on copper alloy Sheets (phosphor bronze) and 6000 series aluminum alloy Sheets (AA6016-T4) were conducted using a specially designed testing apparatus. The apparatus is equipped with comb-type dies so that stress–strain curves of a Sheet Specimen subjected to tension followed by compression, and vice versa, can be measured without buckling of the Specimen, as well as those for monotonic tension and compression. A difference was observed in the flow stresses between tension and compression for the as-received copper alloy, but not for the aluminum alloy. Moreover, stress reversal tests, such as tension followed by compression and compression followed by tension, were carried out in order to measure the Bauschinger effect. In the second part of the experiment, bending moment–curvature diagrams were measured for the as-received and pre-stretched Specimens. The bending moment–curvature diagrams were compared with those calculated using the stress–strain curves obtained from the tension–compression tests, and were in good agreement with those calculated with the tension–compression asymmetry and the Bauschinger effect correctly reproduced.
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tension compression asymmetry of sus304 stainless Sheet for electronic parts and its effects on bending and springback behavior
Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2009Co-Authors: Toshihiko Kuwabara, Rena Saito, Takaaki Hirano, Nobuaki OohashiAbstract:In-plane tension and compression experiments on an austenitic stainless steel Sheet SUS304 0.3 mm in thickness for electronic parts were conducted using a specially designed testing apparatus. The apparatus is equipped with comb-type dies so that stress–strain curves of a Sheet Specimen subjected to tension followed by compression, and vice versa, can be measured without buckling of the Specimen, as well as those for monotonic tension and compression. A difference was observed in the flow stresses between tension and compression for the test material both in the rolling and transverse directions. Moreover, stress reversal tests, such as tension followed by compression and compression followed by tension, were carried out in order to measure the Bauschinger effect. In the second part of the experiment, bending moment–curvature diagrams were measured both in the rolling and transverse bending. The bending moment–curvature diagrams were compared with those calculated using the stress–strain curves obtained from the tension–compression tests, and were in good agreement with those calculated with the tension–compression asymmetry and the Bauschinger effect correctly reproduced.
Viggo Tvergaard - One of the best experts on this subject based on the ideXlab platform.
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effects of texture on shear band formation in plane strain tension compression and bending
International Journal of Plasticity, 2007Co-Authors: Mitsutoshi Kuroda, Viggo TvergaardAbstract:Abstract In this study, effects of typical texture components observed in rolled aluminum alloy Sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain is characterized in terms of an elastic–viscoplastic continuum slip constitutive relation. First, a simple model analysis in which the shear band is assumed to occur in a weaker thin slice of material is performed. From this simple model analysis, two important quantities regarding shear band formation are obtained: i.e. the critical strain at the onset of shear banding and the corresponding orientation of shear band. Second, the shear band development in plane strain tension/compression is analyzed by the finite element method. Predictability of the finite element analysis is compared to that of the simple model analysis. Third, shear band developments in plane strain pure bending of a Sheet Specimen with the typical textures are studied. Regions near the surfaces in a bent Sheet Specimen are approximately subjected to plane strain tension or compression. From this viewpoint, the bendability of a Sheet Specimen may be evaluated, using the knowledge regarding shear band formation in plane strain tension/compression. To confirm this and to encompass overall deformation of a bent Sheet Specimen, including shear bands, finite element analyses of plane strain pure bending are carried out, and the predicted shear band formation in bent Specimens is compared to that in the tension/compression problem. Finally, the present results are compared to previous related studies, and the efficiency of the present method for materials design in future is discussed.
Julian M Allwood - One of the best experts on this subject based on the ideXlab platform.
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design and use of a novel sample design for formability testing in pure shear
Journal of Materials Processing Technology, 2010Co-Authors: D R Shouler, Julian M AllwoodAbstract:Abstract Existing tests for assessing the formability of Sheet metal samples can create strain ratios in the range from uniaxial to biaxial stretching, −1/2 ≤ ɛ2/ɛ1 ≤ 1. A novel sample design is proposed, with shaped cut-outs in a rectangular Sheet Specimen, intended to produce with strain ratios in the range, −1 ≤ ɛ2/ɛ1 ≤ 1/2 in a small zone, while the sample is uniaxially extended. The strain ratio is controlled by changing the geometry of the cut-outs. The behaviour of the new sample design is examined by finite element modelling showing nearly proportional behaviour in the test zone, with the best results occurring near to pure shear. Two experimental methods are considered for the validation of these predictions: measurement of the distortion of a grid of small circles created on the sample surface by laser-scribing; use of a commercial strain measurement system based on an applied speckle pattern. Both techniques demonstrate that the evolution of experimentally measured strains during the test closely follows that predicted numerically. The novel sample is applied to test the formability of a range of materials known to be difficult to form. The tests on aluminium alloys Al 2024, Al 7075, Al 2198 and commercially pure titanium demonstrate that significantly enhanced deformation prior to failure is possible with loading near to pure shear. The implication of these results is that it may be possible to design novel forming processes capable of creating more dramatic deformation in “difficult to form” materials through the creation of strain paths close to pure shear.